Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
OPERATING ACTIVITIES:
Net income (loss)	$ (56,828)	$ 420,427	$ 706,563
Adjustment for loss from discontinued operations	3,838	47	47
Income (loss) from continuing operations	(52,990)	420,474	706,610
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation	598,587	608,039	523,984
Asset impairment charge	6,250	39,242
Amortization of debt issuance costs	1,168	749	400
Provision for (recovery of) bad debt	(2,013)	6,034	(200)
Stock-based compensation	24,383	25,195	26,703
Pension settlement charges	4,964	2,873	1,376
(Gain) loss on investment securities	25,989		(45,234)
Income from asset sales	(9,896)	(11,834)	(19,083)
Deferred income tax expense	60,088	131,431	26,132
Other	151	(368)	1
Change in assets and liabilities:
Accounts receivable	72,792	259,024	(70,458)
Inventories	1,944	(23,052)	(16,623)
Prepaid expenses and other	(2,460)	(4,457)	(12,862)
Accounts payable	(10,907)	(38,983)	(16,104)
Accrued liabilities	49,562	(24,756)	35,378
Deferred income taxes	2,769	688	(749)
Other noncurrent liabilities	(16,831)	38,322	(10,142)
Net cash provided by operating activities from continuing operations	753,550	1,428,621	1,129,129
Net cash provided by (used in) operating activities from discontinued operations	47	(47)	(47)
Net cash provided by operating activities	753,597	1,428,574	1,129,082
INVESTING ACTIVITIES:
Capital expenditures	(257,169)	(1,131,445)	(951,536)
Purchase of short-term investments	(57,276)	(45,607)
Proceeds from sale of short-term investments	58,381
Proceeds from asset sales	21,845	22,643	30,176
Proceeds from sale of investments			49,205
Net cash used in investing activities	(234,219)	(1,154,409)	(872,155)
FINANCING ACTIVITIES:
Payments on long-term debt	(40,000)	(40,000)	(115,000)
Proceeds from senior notes, net of discount		497,125
Debt issuance costs	(1,111)	(5,474)
Proceeds on short-term debt		1,002
Payments on short-term debt		(1,002)
Repurchase of common stock		(59,654)
Dividends paid	(300,152)	(298,367)	(264,386)
Exercise of stock options, net of tax withholding	1,040	2,650	23,250
Tax withholdings related to net share settlements of restricted stock	(3,912)	(5,140)	(3,049)
Excess tax benefit from stock-based compensation	934	3,772	26,616
Net cash provided by (used in) financing activities	(343,201)	94,912	(332,569)
Net increase (decrease) in cash and cash equivalents	176,177	369,077	(75,642)
Cash and cash equivalents, beginning of period	729,384	360,307	435,949
Cash and cash equivalents, end of period	$ 905,561	$ 729,384	$ 360,307